1. Field of the Invention
The present invention relates to a white light emitting diode used in LED display, back light source, traffic signal, indicator, etc. and in particular to a Tri-color ZnSe white light emitting diode.
2. Description of the Related Art
The light emitting diode (LED) has the advantages of being electricity-saving, high reliability, recyclable, and safety. Thus it has been used widely in applications such was various indicators and various light sources. Recently light emitting diode for RGB(red, green and blue) colors having ultra-high luminance and high efficiency have been developed; and large screen LED displays using these light emitting diode have been put into use. The LED display can be operated with less power and has such good characteristics as light weight and long life, and is therefore expected to be more widely use in the future.
A traditional method of manufacturing white light emitting diode, is to use at least two chips to emit different wavelength light, mixing the different wavelength light to produce white light emitting diode.
The method has a following drawbacks
                1. The at least two chips must be packaged at the same time, thus, the manufacturing processes is complicated and the manufacture cost is high.        2. Since the material of each chip for different color of diode is different, the forward voltage (Vf) of every chip is different, therefore, the circuit of the each chip must add the different forward circuit to adjust its brightness and color.        
Furthermore, a traditional method of manufacturing white light emitting diode, is to provide a fluorescent powder coated on the surface of LED chip. The fluorescent powder is capable of absorbing a part of light emitted by LED chip (as blue light et.) and emitted light of a wavelength different from that of the absorbed light to produce another kind of color light. Mixing the emitted light and the absorbed light to produce white light.
Please refer to FIG. 1. It is a diagram showing a traditional emission spectrum of ZnSe white light emitting diode. The method of manufacturing white light emitting diode is to use blue emission layer to produce blue light, which shines a ZnSe chip to produce yellow light, mixing blue light, yellow light to produce white light emitting diode.
Please refer to FIG. 2. It is a cross-sectional view showing a traditional ZnSe white light emitting diode lamp includes a SnZe blue emission layer 1, a ZnSe LED chip 2, wires 3, a lead frame 4, compound resin 5, and an electrode pads 6. The ZnSe LED chip 2 is mounted to the lead frame 4. The SnZe blue emission layer1 is formed on the ZnSe LED chip 2. Wires 3 are electrically connected the electrode pads 6 to the lead frame 4. The compound resin 5 is covered onto the SnZe LED chip 2. So the blue light emitted form the blue emission layer 1 shines the ZnSe LED chip 2 to produce yellow light, mixing blue light and yellow light to produce white light.
At present time, a mixing light is used to white light, which is providing a yellow fluorescent coated on the surface of a blue LED chip to emit yellow light. Mixing the yellow light and the blue light produces white light. For example, the patent of a white light emitting diode (U.S. Pat. No. 5,998,925) of Nichia corporation.
Further, a method of manufacturing mixing light is to mix a red fluorescent powder, blue fluorescent powder, and green fluorescent powder coated on a purple LED chip with a wavelength ranging from 360 nm to 390 nm to produce white light or various color, of light. For example, the patent of U.S. Pat. No. 5,952,684 of Solidlite corporation.